It's still free, no one is forced to use this. Companies exists to make a profit, if Facebook offers something for free of course it's not driven by philanthropy. I believe internet.org is better than no internet at all. Hopefully people in developing countries will be offered alternative in the near future but to get normal internet they need to earn enough to pay for it - internet.org is free with means people using it are the product.
Then I would go for another ISP, that's the point I can choose because I live in Europe, but If I could choose between no internet and free internet from Facebook I would go for free from Facebook if noone else want to provide internet for people in Africa.
Internet.org runs on top of existing ISPs. Anywhere it's accessible, other ISPs are available in the same region too.
"No internet" vs "Internet.org" as the only two options, is not a choice anywhere at all.
Those ISPs have bought public spectrum to provide telecom and internet services. Public spectrum being used to make services of foreign companies free, while making other traffic expensive, is something a democratic population should be concerned about.
This is about not deceiving users and attempting to usurp the definition of the word "Internet". It'd be fine if they called it Facebook Net or whatever.